The present invention relates generally to butt welding railway rails in axially aligned relation, and more particularly to a novel method and apparatus for flash butt welding adjacent ends of axially aligned railway rails which result in substantially improved quality and repeatability of welds.
Welding apparatus for butt welding lengths of railway rails in end-to-end relation to create a relatively long continuous length rail, such as up to approximately one-quarter mile in length, are generally known. See, for example, U.S. Pat. No. 4,103,139. A significant drawback in known apparatus and methods for flash butt welding railway rails is that the quality of the welds is highly operator dependent. As a result, weldments between adjacent ends of different sections of a continuous length rail may vary significantly both as to the quality of weld and the upset distance of the abutting rail ends.
In attempting to assure high quality welds between adjacent sections of rail which make up a longer length continuous rail, the railroad industry is primarily concerned with the amount of heat put into the adjacent rail ends during a weld, and the forging or upset distance which the rail ends undergo during final forging together. To this end, the railroads have set specifications for compliance by the rail manufacturers. These specifications include the forging pressure to be employed for a particular rail chemistry, that is, the particular metallurgical composition of the rails, and the rail transverse cross-section size. The specifications also specify a maximum upset or forging distance range for the rail ends during final forging. These factors (forging pressure and upset or forging distance) dictate the amount of heat which may be put into the rail ends during welding.
Thus, controlling the heat (i.e. electrical power in amp-seconds) put into the ends of the rails during butt welding is critical to meeting the specifications of the railroads. The manner of inputting the welding heat into the adjacent rail ends is equally important so as to prevent burning of the rail end surfaces, the creation of craters or voids in the end surfaces, and/or the formation of oxides which can be captured in the weld. Any of these latter factors can significantly reduce weld integrity and lead to premature failure of the weld joint.